In recent years, there have been proposed data sharing systems in which, when a change is made on a displayed image by an application such as Virtual Network Computing (VNC) at any of multiple information processing devices connected via a network, a difference between images is transferred to the other information processing devices so that images displayed thereon are made to be the same.
In such a system, however, when a change is made on an image displayed on a certain information processing device and difference information of the image is transferred to the other information processing devices, a loop is caused in which displayed images at the other information processing devices are changed according to the received difference information and the other information processing devices thus further transfer difference information of the changes to the certain source information processing device. There is thus a problem that the performances of the information processing devices and the network are degraded owing to occurrence of such a loop of transfer.